In a conventional cellular communication network, the spectrum used by the network for communication services is divided into several portions, and these portions are assigned to geographic cells in accordance with a reuse scheme. The reuse scheme defines how the spectrum portions are "reused" in spaced apart cells. Cells located near one another are assigned different spectrum portions so that no interference occurs in these cells. The network components are configured to limit the range of their communication signals so that interference is prevented in cells to which common spectrum portions are re-assigned.
In conventional cellular communication networks, mobile subscriber units are free to move about, but the cells typically do not move. Over the years, a significant body of equipment, such as mobile telecommunication switching offices (MTSOs), has been developed to support conventional cellular communication networks. In some networks, such as the Groupe Special Mobile (GSM) network, MTSOs keep track of the mobile units that are within their jurisdictions. When mobile units travel to new cells, they inform the system of their presence, and the MTSO updates a code that identifies the cell where the mobile unit is now located. Thus, when an incoming call for the mobile unit occurs, the system knows in which cell to transmit ring signals.
This conventional scheme adequately achieves the goals of cellular communication networks in which cells are static. The network needs to expend spectrum resources only in the cell where a mobile unit resides rather than over the entire service area covered by the network. In addition, only a small amount of memory and processing resources are consumed in maintaining current MTSO records for mobile unit locations and in identifying where to direct incoming calls.
However, when a cellular communication network uses cells that move relative to the earth, the conventional scheme for tracking mobile unit locations becomes impractical. When cells move, all mobile units find themselves in new cells from time to time regardless of any mobile unit movement. If a conventional scheme were used, the amount of overhead resources required to keep the system informed of the cells within which each subscriber unit resides would be excessive because all mobile units would incessantly consume network resources informing the system of their locations.